In Linux, Index Nodes describe file system objects such as files or directories. Each index node stores the attributes and disk block locations of the object's data. In our system, an index node io::fs::IdxNode has 12 direct blocks (a block is a disk sector) and a single indirect block table, which is one sector large and contains 128 block LBAs. So an index node can save up to
bytes.
Index nodes do not indicate their data type. Instead, we use directory entries io::fs::DirEntry to determine whether an item is a file or a directory.
The Super Block is the "configuration" of a file system. It is created when the file system is created for a disk partition. Its size is 4096 bytes and starts at offset 4096 bytes in a partition, behind the boot sector. The following diagram shows a disk's partitions.
block-beta
block
MBR part1["Partition"] ... part2["Partition"]
end
In our system, the internal structure of a partition is:
block-beta
block
boot["Boot Sector"] super_block["Super Block"] block_bitmap["Block Bitmap"] inode_bitmap["Index Node Bitmap"] inodes["Index Nodes"] root_dir["Root Directory"] Blocks
end